ONU management method and optical line termination

ABSTRACT

In a PON system, a PON-ID assigned to a connected ONU before replacement is assigned to a newly connected ONU after the replacement and, setting data before the replacement is succeeded also after the replacement. An OLT includes a PON-ID state where a management state of the PON-ID is stored, a PON-ID management table where the PON-ID and an ONU serial number of the connected ONU and setting data are correspondingly stored and, a delete ONU table where the PON-ID and an ONU serial number of a replacement object are correspondingly stored. When the OLT receives an ONU replacement instruction from an operation system, the PON-ID assigned to the ONU of the replacement object is assigned to an ONU newly connected during the ONU replacement.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an Optical Network Unit (ONU)management method and an optical line termination, and particularly toan ONU management method and an optical line termination in a PassiveOptical Network (PON) system including an Optical Line Termination (OLT)and an ONU or an Optical Network Termination (ONT).

2. Description of the Related Art

At present, as a realization method of an access network with high speedbroad band, the introduction of a PON system has been advanced. The PONsystem is a network system in which plural user side units (ONU: OpticalNetwork Unit) and one station side unit (OLT: Optical Line Termination)are connected in star configuration by an optical splitter and opticalfibers, and communication is performed between the units of the OLT-ONU.

As the PON system, an ATM-PON system in which communication is performedin a PON section based on an Asynchronous Transfer Mode (ATM)communication system is standardized by the ITU-T Recommendation G.983series (see, for example, the ITU-T Recommendation G.983.1). Besides, aGigabit-capable Passive Optical Networks (GPON) system is standardizedby the ITU-T Recommendation G.984 series.

For example, in the ATM-PON system, as described in the ITU-TRecommendation G.983.1, in order to establish communication betweenOLT-ONU and to perform ONU connection, a series of processings calledthe ranging flow is performed. The ranging flow processing is such afunction that distances between OLT-ONU are measured, transmissiontimings of up signals from the ONUs to the OLT are determined for therespective ONUs, and collision of the up signals is prevented. When thedistances are measured in the ranging flow processing, in order toprevent the collision of ONU responses at the time of the measurement,it is necessary to cause the ONUs to respond one by one. For thatpurpose, a unique serial number of the ONU is used. That is, the ONUserial number is designated to specify the ONU which may respond. In theOLT, a number (identifier) for ONU identification, called a PON-ID, isassigned to an ONU whose ONU serial number has been found and whosedistance has been also measured, and after that, the ONU is specified bythe PON-ID, and a message is exchanged between the OLT-ONU.

Although the ONU identifier is described as “PON-ID” in theafter-mentioned ITU-T Recommendation G.983.1, there is a case where itis described as “ONT-ID” or “ONU-ID” according to documents.

The unique serial number of the ONU is defined by information of 64bits, and it is defined such that the 32 upper bits indicate a vender ID(fixed value for each vender) to represent a vender, and the 32 lowerbits indicate a vender definition part which can be arbitrarily definedby the vender. For example, in the vender definition part of 32 bits,“manufacturing date and serial number are assigned”, or “all of the 32bits are made serial number”, so that the respective ONUs have differentserial numbers and the ONUs can be identified.

In the ranging flow processing, the ONU connection is performed usingthe unique serial number of the ONU. As the ONU connection method, forexample, two methods (Method A, Method B) are described in 8.4.1.1 ofthe ITU-T Recommendation G.983.1. The Method A is a method in which forexample, the serial number of the ONU is registered from an operationsystem (OpS) to the OLT. The Method B is a method in which for example,the serial number of the ONU is not registered from an operation systemto the OLT.

In the case of the Method B, although the ONU serial number is notregistered to the OLT from the operation system, in order to establishthe communication between the OLT-ONU, it is necessary for the OLT sideto specify the serial number of the ONU. Thus, a procedure is requiredin which the OLT side searches for the ONU serial number. The search ofthe ONU serial number is such that various bit patterns (for example,several lower bits, etc.) are simply tried among 64-bit patterns of theONU serial number, and the bit pattern consistent with the serial numberof the connected ONU is found by the presence/absence of the responsefrom the ONU. The ITU-T Recommendation G.983.1 III.2 describes anexample of the search method of the ONU serial number.

Besides, there is known a system in which when a current system ofplural ONUs constituting a redundant configuration and a spare systemare switched over, a switch at the ONT side is set, so that the same ONUidentifier is used after and before the switching (see, for example,JP-A-2005-45566). There is also known a system in which in a redundantconfiguration, a current system and a spare system have the samesubscriber unit information (serial number) (see, for example,JP-A-2003-244179).

When the ranging flow processing is performed and the PON-ID is assignedto the connected ONU, the subsequent message between the OLT-ONU isexchanged by specifying the ONU with the PON-ID. Thus, in the case wheresetting is performed individually for the ONU, it is expected that theindividual setting data is correlated with the PON-ID and is stored.Under such circumstances, for example, in the case where a failureoccurs in an ONU, and the ONU is replaced, it is desired that the PON-IDassigned before the replacement is assigned also to an ONU after thereplacement, and the individual setting data before the replacement issucceeded and set.

According to the ITU-T Recommendation G. 983.1, the procedure of the ONUreplacement is not specified. In case the Method A of the ITU-TRecommendation G. 983.1, that is, the method of previously registeringthe ONU serial number from the OLT is adopted, since the serial numberof the new ONU is known at the OLT side also at the time of the ONUreplacement, the ONU serial number of the storage data has only to berewritten. However, in order to actually perform this method, it isnecessary to perform such complicated management that at the time of theONU replacement, an ONU installation worker and an operation systemadministrator communicate with each other in real time, and the new ONUserial number is inputted from the operation system to the OLT, or theONU serial number is previously informed to the operation systemadministrator, and the ONU with the serial number is certainlydistributed to the user as the replacement destination.

In case the Method B of the ITU-T Recommendation G.983.1, that is, themethod in which the ONU serial number is not registered from the OLT isadopted, the OLT searches for the ONU serial number by some method andautomatically performs the ONU connection. At this time, when the ONU issimply replaced and the new ONU is connected, the PON-ID is newlyassigned, and the storage data before the replacement can not besucceeded. Alternatively, it becomes necessary to manually set dataagain.

Besides, in the method disclosed in JP-A-2005-45566, the setting of theswitch and the like are required at the ONU side. In the methoddisclosed in JP-A-2003-244179, it is necessary that the current systemand the spare system have the same serial number.

In view of the above circumstances, the present invention has an objectto provide an ONU management method and an optical line termination, inwhich in a PON system, ONU connection is performed without registering aserial number of an ONU from an operation system to an OLT, and the samePON-ID as that before the ONU is replaced is assigned to a new ONU afterthe replacement. Besides, another object of the invention is thatsetting data before replacement is succeeded also after the replacement.

Another object of the invention is to eliminate the necessity that in aPON system, at the time of ONU installation or replacement, an ONUinstallation worker and an operation system administrator communicatewith each other in real time, and an ONU serial number is inputted froman operation system to an OLT. Besides, another object of the inventionis to eliminate the necessity that ONU setting data is set again afterONU replacement, and to enable the ONU replacement to be facilitated.

SUMMARY OF THE INVENTION

In order to achieve the above objects, in a PON system and an ONUmanagement method of the invention, an OLT includes an area (PON-IDstate) where a management state of a PON-ID is stored, an area (PON-IDmanagement table) where the PON-ID and a serial number of a connectedONU are made to correspond to each other and are stored, and an area(delete ONU table) where the PON-ID and an ONU serial number of a deleteobject are made to correspond to each other and are stored, and when anONU replacement instruction is received, the PON-ID management state isset to be under ONU replacement, the PON-ID is stored, the PON-IDassigned to the ONU of the replacement object is assigned to an ONUnewly connected during the ONU replacement, and the PON-ID before thereplacement is assigned to the ONU after the replacement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of the whole system configuration of a PONsystem.

FIG. 2 is a block configuration view showing an example of an OLT.

FIG. 3 shows an example of a structure of a PON-ID management table.

FIG. 4 shows an example of a structure of a delete ONU table.

FIG. 5 shows an example of a definition of a PON-ID state.

FIG. 6 shows an example of a flowchart of an ONU connection mainprocess.

FIG. 7 shows an example of a flowchart of an ONU connection process.

FIG. 8 shows an example of a flowchart of the ONU connection process.

FIG. 9 is a flowchart showing the outline of a ranging flow processingin the ITU-T Recommendation G.983.1.

FIG. 10 shows an example of a flowchart of an ONU connection recoveryprocess.

FIG. 11 shows an example of a flowchart of an ONU delete process.

FIG. 12 shows an example of a flowchart of an ONU replacement process.

FIG. 13 shows an example of a flowchart of an ONU setting process.

FIG. 14 shows an example of a sequence.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the drawings.

Hard Structure

FIG. 1 shows an example of the whole system configuration of a PONsystem in an embodiment.

The PON system includes, for example, an OLT 40, plural ONUs (60-1 to60-n), an optical splitter 50, and optical fibers 140 and 150. Besides,the PON system can include an operation system (OpS) 10, a switching hub20, an initial setting terminal 80, and subscriber terminals 70.

In FIG. 1, the OLT 40 is connected to the plural ONUs (60-1 to 60-n)through the optical fibers (140, 150-1, 150-n) and the optical splitter50. The optical splitter 50 equally distributes an optical signal, whichhas been transmitted to the optical fiber 140 from the OLT 40, to theplural connected ONUs (60-1 to 60-n). Besides, the optical splittermultiplexes optical signals transmitted from the plural ONUs (60-1 to60-n) to the optical fibers (150-1 to 150-n) and transfers them to theOLT 40. The respective ONUs (60-1 to 60-n) are connected to thesubscriber terminals (70-1 to 70-n) through lines (160-1 to 160-n) ofEthernet (registered trademark) or the like.

The ONU may be an optical network termination such as an ONT. The PONsystem may include plural OLTs 40 and 41. At this time, the ONUs, theoptical fibers and the optical splitter are provided for each of theOLTs as shown in FIG. 1.

The operation system 10 to perform the management and setting of the PONsystem is connected to the OLTs (40, 41) through lines (100, 110, 111)of Ethernet (registered trademark) or the like and the switching hub 20to perform transfer of Ethernet (registered trademark) frames.

The initial setting terminals (80, 81) can be used for performing, asthe pre-stage of connection of the operation system 10, initial settingof various parameters and the like at the time of initial setting of theOLTs (40, 41), and is connected to the OLTs through, for example, lines(130, 131) of serial cables or the like.

The OLTs (40, 41) are connected to the Internet 30 through lines (120,121) of Ethernet (registered trademark) or the like, and enableprovision of services, such as Internet access, to the subscriberterminals (70-1 to 70-n, 71-1 to 71-n).

For example, in the ATM-PON system, the ONUs (60-1 to 60-n, 61-1 to61-n) are installed, and before the services are started to thesubscriber, in order to establish communication between the OLTs (40,41)—ONUs (60-1 to 60-n, 61-1 to 61-n), ONU connection is performed inaccordance with, for example, the procedure described in the ITU-TRecommendation G.983.1. In the case where the Method B of the ITU-TRecommendation G.983.1 is used for the connection of the ONU, it isnecessary that the OLT searches for the ONU serial number (uniquenumber) to specify the serial number of the ONU, and performs theconnection. In this embodiment, also at the time of replacement of theONU due to an ONU failure or the like, the serial number of the ONUafter the replacement is not registered from the OLT, and the ONUconnection is automatically performed.

In the following description, although the ATM-PON system will bedescribed as an example, the invention can be similarly applied toanother system such as a GPON system.

FIG. 2 is a block configuration view showing an example of the OLT 40 inthis embodiment. The OLT 40 shown in FIG. 2 includes a control networkinterface unit 410 connected to the operation system 10 or the switchinghub 20, a main signal network interface unit 420 connected to theInternet 30, a serial interface unit 430 connected to the initialsetting terminal 80, an optical interface unit 490 connected to the ONU60 through, for example, the optical fiber 140 and the optical splitter50 and including E/O conversion and O/E conversion, a PON control unit480 connected to the optical interface unit 490 and to perform a PONcontrol, and an OLT control unit 440 to perform a control of the OLT.

The OLT control unit 440 includes a CPU 450, a non-volatile memory 460,and a volatile memory (RAM) 470. As the non-volatile memory 460,although a flash memory can be used as an example, an EPROM (ErasableProgrammable ROM) or an EEPROM (Electro Erasable Programmable ROM) maybe used.

The non-volatile memory 460 stores, for example, a program code 461, aPON-ID state (state management unit) 462, a PON-ID management table(connection management table) 463, and a delete ONU table (deletemanagement table) 464. The program code 461 is an OS or an applicationto be executed by the CPU 450, and at the time of start, it is loadedfrom the non-volatile memory 460 into the volatile memory 470. A maincontrol process 471, an ONU connection main process 472, an ONUconnection recovery process 473, an ONU delete process 474, an ONUreplacement process 475, an ONU connection process 476, an ONU settingprocess 477 and the like are part of the program code 461. The maincontrol process 471 is a main routine to perform an OLT control, andstarts the ONU connection main process 472 as the need arises. Therespective processes will be described later in detail.

Memory Structure

FIG. 3 shows an example of the structure of the PON-ID management table463 in this embodiment. The PON-ID management table 463 is such a tablethat in this embodiment, an ONU serial number is searched, and the foundONU serial number is made to correspond to “PON-ID” and is stored.

In FIG. 3, the PON-ID management table 463 includes a flag area 4631 toindicate whether the PON-ID has been already assigned, an area 4632 tostore the serial number of the ONU 60 to which the PON-ID is assigned,and an area 4633 where individual setting for the ONU is stored. Theindividual setting includes a setting parameter necessary for providingservices to a user by using the ONU 60, and management data used for theONU management, and any information and data may be used. As an exampleof the individual setting, the setting of, for example, a maximumbandwidth assigned to the ONU 60, a network address (IP address), a username of the ONU 60 and the like are conceivable. In addition to these,suitable information concerning the communication of the ONU and/or usermay be used.

In the example of FIG. 3, an area to store the PON-ID itself is notprovided. This is because when the memory address and the PON-ID aremade to correspond to each other, the area to store the PON-ID is notrequired. Here, the PON-ID is an identifier (ID) to specify the ONU 60as a message object uniquely when a message is sent from the OLT 40 tothe ONU 60, and is the ID assigned from OLT 40 at the time of theestablishment of communication between the OLT-ONU and after the serialnumber of the ONU 60 is specified by the OLT 40. Since the example ofFIG. 3 is a configuration example of a case in which 64 (0 to 63) ONUsat the maximum are connected, the areas up to PON-ID #63 are shown. Anarea to store the PON-ID may be provided.

With respect to the PON-ID assignment flag 4631, an example is shown inwhich in the case where the PON-ID has already been assigned, the value“1” is stored, and in the case of not assigned, the value “0” is stored.However, a method in which the PON-ID assignment flag 4631 is notprovided can be adopted by making such a definition that in the case ofnot assigned, a value (for example, all are 0 or null code) previouslydetermined in the ONU serial number storage area 4632 is stored.

FIG. 4 shows an example of the structure of the delete ONU table 464 inthis embodiment. The delete ONU table 464 is such a table that in thisembodiment, when an ONU delete instruction or an ONU replacementinstruction is received from the operation system 10 or the initialsetting terminal 80, the serial number of the ONU as the delete orreplacement object is made to correspond to the “PON-ID” and is stored.Although the ONU delete instruction from the operation system 10 or theinitial setting terminal 80 can be performed with the PON-ID, it may beperformed with the ONU serial number itself. In FIG. 4, the delete ONUtable 464 includes a delete object ONU serial number storage area 4641as an area to store the ONU serial number of the delete or replacementobject.

In the example of FIG. 4, an area to store the PON-ID itself is notprovided. This is because when the memory address and the PON-ID aremade to correspond to each other, the area to store the PON-ID is notrequired. Since the example of FIG. 4 is the structural example of thecase in which 64 (0 to 63) ONUs at the maximum are connected, the areasup to PON-ID #63 are shown. An area to store the PON-ID may be provided.

In the delete object ONU serial number storage area 4641, for example,in the case where the instruction of “deletion of ONU of PON-ID #3” isreceived from the operation system 10, the ONU serial number to whichthe PON-ID #3 is assigned is stored into the area corresponding toPON-ID #3. A previously determined value (for example, all are 0 or nullcode) is stored in the area corresponding to the PON-ID which is beingused (delete or replacement instruction is not received). Incidentally,for example, the operation system 10 receives the notification of ONUreplacement from a subscriber or the like, and can specify the PON-ID.

For example, a time lag can occur between the time when the OLT 40receives the replacement instruction from the operation system 10 andthe time when the ONU installer actually removes the ONU as thereplacement object and connects a new ONU. Since the OLT 40 periodicallysearches for a serial number also in this period, in the state where theserial number is deleted from the PON-ID management table 463, the ONUbefore the replacement is recognized as the new ONU, and the connectionprocessing is performed. Then, the OLT 40 refers to the ONU deletiontable 464, and in the case where the searched serial number is stored,it is regarded as the serial number of the ONU of the replacement objector delete object, and the connection processing or the like is notperformed.

FIG. 5 is an explanatory view of an example of the definition of thePON-ID state 462 in this embodiment. In this embodiment, the PON-IDstate 462 takes one of three states of “ONU is being replaced”, “thereis PON-ID to be assigned” and “there is no PON-ID to be assigned”, andindicates the management state of the PON-ID.

The example of FIG. 5 is the example of the case in which 64 ONUs at themaximum are connected, and it is defined that the PON-ID state 462indicating “ONU is being replaced” takes, for example, a value of 0 to63. That is, the case of “PON-ID state 462=3” means such a situationthat the replacement instruction of PON-ID #3 is received, and thereplacement has not yet been ended. Besides, it is defined that in thecase where the 64 ONUs are connected, and the assignment of PON-ID #0 to#63 has been completed, the state is made “there is no PON-ID to beassigned”, and a value “255” is taken. Further, it is defined that inthe case where less than 64 ONUs are connected, the state is made “thereis PON-ID to be assigned”, and a value of from “64” to “254” is taken.Incidentally, suitable values other than the above values can be definedas the values corresponding to the respective states.

Flowchart

Next, the operation of this embodiment will be described.

FIG. 6 shows a flowchart of an example of the ONU connection mainprocess 472 in this embodiment. The ONU connection main process 472 is aprocess to perform new connection, deletion, replacement, and connectionrecovery of an ONU.

The ONU connection main process 472 is started from the main controlprocess 471 at the time of OLT start. In the following description,respective processes can be executed by the CPU 450. In addition to thisprocess, the CPU 450 receives instructions of “ONU deletion”, “ONUreplacement”, “ONU setting” and the like at suitable timing. Theseinstructions can be stored in, for example, a queue.

In the ONU connection main process 472, the PON-ID management table 463is searched, and it is judged whether or not at least one PON-ID hasalready been assigned (S1 of FIG. 6). In the case where the assignmenthas already been made, the information stored in the PON-ID managementtable 463 is used, and the ONU connection recovery process 473 isexecuted to recover the ONU connection (S2 of FIG. 6).

Since the ONU connection recovery process 473 is the process in whichthe connection at the time of the former start is recovered at the timeof OLT start, it has only to be performed once at the time of the OLTstart.

Next, in the ONU connection main process 472, it is judged whether ornot the “ONU deletion” instruction is received from the operation system10 or the initial setting terminal 80 (S3 of FIG. 6). In the case wherethe “ONU deletion” instruction is received, the ONU delete process 474is executed (S4 of FIG. 6).

Next, it is judged whether or not the “ONU replacement” instruction isreceived from the operation system 10 or the initial setting terminal 80(S5 of FIG. 6). In the case where the “ONU replacement” instruction isreceived, the ONU replacement process 475 is executed (S6 of FIG. 6).

Next, the PON-ID state 462 is read, and it is judged whether or not thePON-ID state 462 indicates “there is PON-ID to be assigned” or “ONU isbeing replaced” (S7 of FIG. 6). In this embodiment, as shown in FIG. 5,it is judged whether the PON-ID state has a value of 64 to 254. In thecase where the PON-ID state 462 indicates “there is PON-ID to beassigned” or “ONU is being replaced”, the ONU connection process 476 isexecuted (S8 of FIG. 6). In the case where the PON-ID state 462indicates “there is no PON-ID to be assigned”, it means that the ONUs upto the maximum number are connected.

Next, it is judged whether or not the “ONU setting” instruction isreceived from the operation system 10 or the initial setting terminal 80(S9 of FIG. 6). In the case where the “ONU setting” instruction isreceived, the ONU setting process 477 is executed (S10 of FIG. 6).

Next, in the ONU connection main process 472, return is made to thejudgment (S3 of FIG. 6) as to whether or not the “ONU deletion”instruction is received, and the subsequent processing is repeated. Byrepeating this processing, the ONU connection main process can deal withthe additional connection, replacement, deletion, and setting of an ONUwhich is being used.

Incidentally, the order of the processing of S3, S5, S7 and S9 of FIG. 6may be changed.

FIGS. 7 and 8 show flowcharts of an example of the ONU connectionprocess 476. The ONU connection process 476 of step S8 is the process toperform the new connection of the installed ONU. FIG. 9 is a roughflowchart up to the ONU connection in the ranging flow processingdescribed in the ITU-T Recommendation G.983.1. Since the ranging flow isdescribed in the ITU-T Recommendation G.983.1, its explanation will beomitted.

In the ONU connection process 476, a processing up to the ONU serialnumber acquisition (S903 of FIG. 9) is performed in the ranging flowprocessing by the Method B based on the ITU-T Recommendation G.983.1(S801 of FIG. 7). In the ranging flow by the Method B, since the ONUconnection is performed without registration of the serial number of theONU 60 from the OLT 40, the search processing of the ONU serial numberis required. In this embodiment, a known technique can be used as thesearch method of the ONU serial number. Here, when there is a newlyconnected ONU 60, the serial number thereof is acquired.

Next, it is judged whether the ONU serial number has been acquired (S802of FIG. 7). In the case where the ONU serial number has not beenacquired (No route of S802 of FIG. 7), it means that a new ONU has notbeen connected during one cycle of the ONU serial number search, andaccordingly, the ONU connection process 476 is ended.

In the case where the ONU serial number has been aquired (Yes route ofS802 of FIG. 7), it is judged whether or not the acquired ONU serialnumber exists in the delete ONU table 464 (S803 of FIG. 7). In the casewhere the acquired ONU serial number exists in the ONU delete table 464(Yes route of S803 of FIG. 7), since the ONU is the delete object, theONU connection is not performed, and in order to continue the ONU searchprocessing from the subsequent bit pattern, return is made to the ONUserial number search processing (S801 of FIG. 7). For example, in thecase where the ONU itself is still connected although the instruction of“ONU” deletion is received, the serial number search is made by theforegoing ranging flow, however, the connection processing is notpreformed for the ONU. In the case where the acquired ONU serial numberdoes not exist in the delete ONU table 464 (No route of S803 of FIG. 7),since the ONU is a newly connected ONU, the PON-ID state 462 is nextread, and it is judged whether or not the PON-ID state 462 indicates“ONU is being replaced” (S804 of FIG. 8). For example, as shown in FIG.5, it is judged whether the PON-ID state is a value of 0 to 63.

In the case where the PON-ID state 462 indicates “ONU is being replaced”(Yes route of S804 of FIG. 8), the value of the PON-ID state 462 is setto be the PON-ID value which is assigned to the ONU whose serial numberhas now been acquired (S805 of FIG. 8). For example, the PON-ID state462 indicates a value “3”, “3” is set as an “assigned PON-ID value”.

In the case where the PON-ID state 462 does not indicate “ONU is beingreplaced” (No route of S804 of FIG. 8), the PON-ID management table 463is searched, and one of non-assigned PON-ID values is set as the“assigned PON-ID value” (S806 of FIG. 8). The non-assigned PON-ID is thePON-ID indicating that the PON-ID assignment flag 4631 indicates a value“0”. In another method, the connection ONU serial number 4632 of thePON-ID management table 463 is the PON-ID indicating a previouslydetermined value (for example, all are 0 or null code).

Next, the processings (S904 to S906 of FIG. 9) subsequent to the PON-IDsetting of the ranging flow processing described in the ITU-TRecommendation G.983.1 are carried out (S807 of FIG. 8). By theseprocessings, the ONU 60 and the OLT 40 are connected.

Next, in the PON-ID management table 463, a value “1”, which indicatesthat assignment has been made, and the acquired ONU serial number arerespectively stored in the PON-ID assignment flag 4631 and theconnection ONU serial number 4632 at the same PON-ID row as the“assigned PON-ID value”, and the PON-ID management table 463 is updated(S808 of FIG. 8).

Next, in the delete ONU table 464, the delete object ONU serial number4641 at the same PON-ID row as the “assigned PON-ID value” is deleted(initialized) from the table (S809 of FIG. 8). This “S809” processing isa correspondence processing at the time of ONU replacement. In the casewhere the ONU replacement instruction is received, the ONU serial numberas the delete object and before the replacement is stored in the deleteobject ONU serial number 4641 at the PON-ID row of the delete ONU table464. When the ONU replacement is performed, the PON-ID is assigned tothe new ONU after the replacement, and the ONU serial number of thedelete object is deleted from the delete ONU table 464.

Next, the PON-ID management table 463 is searched, and it is judgedwhether there is room for the PON-ID (whether there is non-assignedPON-ID) (S810 of FIG. 8). For example, reference is made to the PON-IDassignment flag, and when there is “0” indicating the non-assignment, itis judged that there is room. In the case where there is room (Yes routeof S810 of FIG. 8), “there is PON-ID to be assigned” and is stored (S812of FIG. 8). In the case where there is no room (No route of S810 of FIG.8), the PON-ID state 462 is made to have a value (for example, 255)indicating “there is on PON-ID to be assigned” and is stored (S811 ofFIG. 8). This is the end of the ONU connection process.

FIG. 10 shows a flowchart of an example of the ONU connection recoveryprocess 473. The ONU connection recovery process 473 of step S2 of FIG.6 is such a process that the OLT is once started and after the ONUconnection is performed, in the case where the OLT is restarted, theconnection of the ONU is recovered in accordance with the setting storedin the past.

In the ONU connection recovery process 473, respective pieces of theinformation of the PON-ID management table 463 are read (S201 of FIG.10). Next, the ranging flow processing (for example, S901, S903 to S906of FIG. 9) by the Method A based on the ITU-T Recommendation G.983.1 isperformed for the ONU 60 to which the PON-ID has been assigned (S202 ofFIG. 10).

Although the ONT connection method in this embodiment is made the MethodB, in the ONU connection recovery process 473, since the ONU serialnumber has already been stored in the PON-ID management table 463, it ispossible to perform the ONU connection by the same procedure as theMethod A.

Next, it is judged whether or not the ranging flow processing has beenperformed for all the ONUs 60 to which the PON-IDs have already beenassigned (S203 of FIG. 10). When there is an ONU 60 to which the PON-IDhas been assigned and whose processing has not been performed (No routeof S203 of FIG. 10), return is made to the processing of S201, and theprocessing is repeated. When the processing has been made for all theONUs to which the PON-IDs have been assigned (Yes route of S203 of FIG.10), the ONU connection recovery process 473 is ended.

FIG. 11 is a flowchart of an example of the ONU delete process 474. TheONU delete process 474 of step S4 of FIG. 6 is a process to delete theregistration of the once connected ONU when the ONU 60 is removed dueto, for example, termination of contract.

The ONU delete process 474 receives, from the operation system 10 or theinitial setting terminal 80, the ONU delete instruction to specify theONU to be deleted. At this time, the way of specifying the ONU of thedelete object may be such that it is specified by the PON-ID, or it isspecified by the ONU serial number, and in the ONU delete process 474,the PON-ID is reversely obtained from the ONU serial number of thePON-ID management table 463.

In the ONU delete process 474, the serial number of the delete objectONU is stored in the PON-ID row of the delete ONU table 464 (S401 ofFIG. 11). As the serial number of the delete object ONU, the serialnumber acquired from the PON-ID management table 463 can be used basedon, for example, the PON-ID specified by the ONU delete instruction.Next, in the PON-ID management table 463, the PON-ID assignment flag4631, the connection ONU serial number 4632, and the individual setting4633 at the PON-ID row as the delete object are initialized (S402 ofFIG. 11).

Next, the PON-ID state 462 is read, and it is judged whether or not thePON-ID state 462 indicates “ONU is being replaced” (S403 of FIG. 11). Inthe case where the PON-ID state 462 does not indicate “ONU is beingreplaced” (No route of S403 of FIG. 11), a vacancy (non-assignment)ought to occur in the PON-ID assignment by the ONU deletion, an updateis made such that the PON-ID state 462 indicates “there is PON-ID to beassigned” (S404 of FIG. 11), and the ONU delete process 474 is ended.

In the case where the PON-ID state 462 indicates “ONU is being replaced”(Yes route of S403 of FIG. 11), the ONU delete process 474 is ended. TheONU replacement process 475 of step S6 of FIG. 6 is a process to replacethe ONU when the ONU goes wrong.

FIG. 12 shows a flowchart of an example of the ONU replacement process475.

In the ONU replacement process 475, the ONU replacement instruction tospecify the ONU to be replaced is received from the operation system 10or the initial setting terminal 80. At this time, the way of specifyingthe ONU of the replacement object may be such that it is specified bythe PON-ID, or it is specified by the ONU serial number, and in the ONUreplacement process 475, the PON-ID is reversely obtained from the ONUserial number of the PON-ID management table 463.

In the ONU replacement process 475, the serial number of the replacementobject ONU is stored in the PON-ID row of the delete ONU table 464 (S601of FIG. 12). As the serial number of the replacement object ONU, basedon the specified PON-ID, a number acquired from the PON-ID managementtable 463 can be used.

Next, in the PON-ID management table 463, the PON-ID assignment flag4631 and the connection ONU serial number 4632at the PON-ID row as thereplacement object are initialized and stored (S602 of FIG. 12). At thistime, since the ONU is replaced, the individual setting 4633 is notinitialized and is held.

Next, the PON-ID state 462 is updated to indicate “ONU is beingreplaced” and is stored (S603 of FIG. 12), and the ONU replacementprocess 475 is ended. For example, the value of the specified PON-ID isstored in the PON-ID state 462.

FIG. 13 is a flowchart of an example of the ONU setting process 477. TheONU setting process 477 of step S10 of FIG. 6 is a process to set andstore individual data relevant to the ONU.

In the ONU setting process 477, data content to be set in the ONU isreceived from the operation system 10 or the initial setting terminal80. The data content includes, for example, a network address, a maximumbandwidth, a user name and the like. At this time, the way of specifyingthe ONU of the data setting object may be such that it is specified bythe PON-ID, or it is specified by the ONU serial number, and the PON-IDis reversely obtained from the ONU serial number of the PON-IDmanagement table 463 in the ONU setting process 477.

In the ONU setting process 477, the data setting is performed for theONU 60 having the PON-ID in accordance with the instruction from theoperation system 10 or the initial setting terminal 80, and the datacontent (S1001 of FIG. 13).

Next, in the ONU setting process 477, the setting content is stored inthe individual setting 4633 at the PON-ID row of the PON-ID managementtable 463 (S1002 of FIG. 13).

FIG. 14 shows an example of the transition sequence of the PON-ID state462, the PON-ID management table 463, and the delete ONU table 464 inaccordance with the flowcharts of the embodiment. In FIG. 14, forsimplification, an explanation will be mad while it is assumed that themaximum connection number of ONUs is two, and the ONU serial number is 1byte.

A state 501 of FIG. 14 indicates an initial state, the PON-ID state 462indicates “there is PON-ID to be assigned”, and the others indicateinitial values. A state 502 of FIG. 14 indicates a state in which oneONU having an ONU serial number 0x0A is connected, the operation isperformed in accordance with the ONU connection process of FIGS. 7 and8, and “XXX” is set as the individual setting in accordance with the ONUsetting process of FIG. 13. A state 503 of FIG. 14 indicates a state inwhich one ONU having an ONU serial number 0x0B is additionallyconnected, the operation is performed in accordance with the ONUconnection process of FIGS. 7 and 8, and “YYY” is set as the individualsetting.

A state 504 of FIG. 14 indicates a state in which the delete instructionof the ONU of PON-ID #1 is made, and the operation is performed inaccordance with the ONU delete process of FIG. 11. In the ONU deleteprocess, the individual setting (XXX) is also deleted. A state 505 ofFIG. 14 indicates a state in which the replacement instruction of theONU of PON-ID #2 is made, and the operation is performed in accordancewith the ONU replacement process of FIG. 12. In the ONU replacementprocess, the individual setting (YYY) is not deleted.

A state 506 of FIG. 14 indicates the result of an operation in which theONU having the ONU serial number 0x0B is replaced by a new ONU having anONU serial number 0x0C, and the operation is performed in accordancewith the ONU connection process of FIGS. 7 and 8. Here, there isindicated a state in which the individual setting data “YYY” before thereplacement is succeeded to the ONU (serial number 0x0C) after thereplacement.

In the embodiment 1, although the ONU management method in the ATM-PONsystem has been described as an example, the invention can be applied toan ONU management method in a GPON system, or another PON system.

According to the embodiment, in the PON system, it is not necessary thatat the time of ONU installation or replacement, an ONU installationworker and an operation system administrator communicate with eachother, and the ONU serial number is inputted from the operation systemto the OLT, or the ONU setting data is set again after the ONUreplacement, and the ONU replacement can be facilitated.

According to the invention, the ONU management method and the opticalline termination can be provided in which in the PON system, the ONUconnection is performed without registering the serial number from theoperation system to the OLT, and the same PON-ID as that before thereplacement of the ONU is assigned to the new ONU. Besides, according tothe invention, the setting data before the replacement can be succeededalso after the replacement.

According to the invention, in the PON system, it becomes unnecessarythat at the time of ONU installation or replacement, the ONUinstallation worker and the operation system administrator communicatewith each other in real time, and the ONU serial number is inputted fromthe operation system to the OLT. Besides, according to the invention, itis not necessary to set the ONU setting data again after the ONUreplacement, and the ONU replacement can be facilitated.

1. An optical line termination in a passive optical network system inwhich each of one or plural first optical network units at user side andthe optical line termination at station side are connected to each otherthrough an optical fiber and a splitter, and communication is performedin accordance with an identifier assigned to each of the first opticalnetwork units connected to the optical line termination, the opticalline termination comprising: a first storage area in which uniquenumbers of the first optical network units and individual settinginformation concerning communication and/or users of the first opticalnetwork units are stored correspondingly to the identifier of the firstoptical network unit; a second storage area in which the unique numberof the first optical network unit which is specified as a replacementobject from among the first optical network units is storedcorrespondingly to the identifier; and a processing unit to perform aprocessing to replace one of the connected first optical network unitsby a second optical network unit, wherein the processing unit receives areplacement instruction including the identifier of the first opticalnetwork unit specified as the replacement object from an operationsystem, acquires the unique number of the first optical network unitcorresponding to the specified identifier from the first storage area,and stores the acquired unique number of the first optical network unitinto the second storage area correspondingly to the specifiedidentifier, deletes the unique number corresponding to the specifiedidentifier from the first storage area, acquires the unique number ofthe first optical network unit or a unique number of the second opticalnetwork unit newly connected instead of the first optical network unit,judges whether the acquired unique number is stored in the secondstorage area, stores, in a case where the unique number of the secondoptical network unit is acquired thereby being judged that the acquiredunique number is not stored in the second storage area, the acquiredunique number into the first storage area correspondingly to thespecified identifier; and repeats, in a case where the unique number ofthe first optical network unit is acquired thereby being judged that theacquired unique number is stored in the second storage area, theacquiring the unique number of the first or the second optical networkunit, the judging and the storing into the first storage area.
 2. Theoptical line termination according to claim 1, wherein the processingunit deletes the unique number corresponding to the specified identifierfrom the second storage area when the unique number is stored in thefirst storage area.
 3. The optical line termination according to claim1, further comprising: a state management unit to be stored informationindicating that the optical network unit is being replaced orinformation indicating presence/absence of the identifier to beassigned, wherein the processing unit stores information, whichindicates that the optical network unit is being replaced in accordancewith the replacement instruction, into the state management unit, andstores, after the replacement, the information indicating thepresence/absence of the identifier to be assigned, and refers to thestate management unit when the unique number is acquired, assigns one ofnon-assigned identifiers in a case where the optical network unit is notbeing replaced, and stores the acquired unique number and the individualsetting information, correspondingly to the identifier into the firststorage area.
 4. The optical line termination according to claim 1,wherein the processing unit receives a delete instruction including theidentifier of the first or the second optical network unit specified asa delete object, acquires the unique number corresponding to theidentifier from the first storage area and stores the unique number intothe second storage area correspondingly to the specified identifier, anddeletes the unique number and the individual setting information,corresponding to the specified identifier from the first storage area.5. An optical line termination in a passive optical network system inwhich each of one or plural first optical network units at user side andthe optical line termination at station side are connected to each otherthrough an optical fiber and a splitter, and communication is performedin accordance with an identifier assigned to each of the first opticalnetwork units connected to the optical line termination, the opticalline termination comprising: a first storage area in which uniquenumbers of the first optical network units and individual settinginformation concerning communication and/or users of the first opticalnetwork units are stored correspondingly to the identifier of the firstoptical network unit; a second storage area in which the unique numberof the first optical network unit which is specified as a replacementobject from among the first optical network units is storedcorrespondingly to the identifier; and a processing unit to perform aprocessing to replace one of the connected first optical network unitsby a second optical network unit, wherein the processing unit receives areplacement instruction including the unique number of the first opticalnetwork unit specified as the replacement object from an operationsystem, acquires the identifier of the first optical network unitcorresponding to the specified unique number from the first storagearea, and stores the specified unique number of the first opticalnetwork unit into the second storage area correspondingly to theacquired identifier, deletes the specified unique number from the firststorage area, acquires the unique number of the first optical networkunit or a unique number of the second optical network unit newlyconnected instead of the first optical network unit, judges whether theacquired unique number is stored in the second storage, stores, in acase where the unique number of the second optical network unit isacquired thereby being judged that the acquired unique number is notstored in the second storage area, the acquired unique number into thefirst storage area correspondingly to the identifier corresponding tothe specified unique number; and repeats, in a case where the uniquenumber of the first optical network unit is acquired thereby beingjudged that the acquired unique number is stored in the second storagearea, the acquiring the unique number of the first or the second opticalnetwork unit, the judging and the storing into the first storage area.